feat(ext/vault): wire vault-status into sidebar footer (Plan C Phase 6)

Renders the status indicator into #vault-status-slot on sidebar mount and on
a manual ↻ button. No timer polling — get_vault_status returns cached state
and sync is user-initiated. Closes the relicario status CLI/extension parity
gap.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

extension/src/vault/__tests__/vault-sidebar-status.test.ts

@@ -0,0 +1,62 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { renderSidebarShell, wireSidebar } from '../vault-sidebar';
+import type { VaultController } from '../vault-context';
+
+const STATUS = { ahead: 0, behind: 0, lastSyncAt: 1700000000, pendingItems: 4 };
+
+function makeCtx() {
+  return {
+    state: { searchQuery: '' },
+    sendMessage: vi.fn(async (req: { type: string }) =>
+      req.type === 'get_vault_status'
+        ? { ok: true, data: STATUS }
+        : { ok: true }),
+    render: vi.fn(),
+    renderPane: vi.fn(),
+    renderListPane: vi.fn(),
+    closeDrawer: vi.fn(),
+    openTypePanel: vi.fn(),
+    setHash: vi.fn(),
+    applyShellViewClass: vi.fn(),
+  } as unknown as VaultController;
+}
+
+function statusCalls(ctx: VaultController): number {
+  return (ctx.sendMessage as ReturnType<typeof vi.fn>).mock.calls
+    .filter((c) => (c[0] as { type: string }).type === 'get_vault_status').length;
+}
+
+describe('vault-sidebar status wiring', () => {
+  beforeEach(() => { document.body.innerHTML = renderSidebarShell(); });
+  afterEach(() => { document.body.innerHTML = ''; });
+
+  it('fetches + renders the indicator on mount', async () => {
+    const ctx = makeCtx();
+    wireSidebar(ctx);
+    await vi.waitFor(() => {
+      expect(document.getElementById('vault-status-slot')?.textContent).toMatch(/4 pending/i);
+    });
+    expect(statusCalls(ctx)).toBe(1);
+  });
+
+  it('re-fetches on the manual refresh button', async () => {
+    const ctx = makeCtx();
+    wireSidebar(ctx);
+    await vi.waitFor(() => expect(statusCalls(ctx)).toBe(1));
+    document.getElementById('status-refresh-btn')?.dispatchEvent(new Event('click'));
+    await vi.waitFor(() => expect(statusCalls(ctx)).toBe(2));
+  });
+
+  it('does NOT poll on a timer', async () => {
+    vi.useFakeTimers();
+    try {
+      const ctx = makeCtx();
+      wireSidebar(ctx);
+      await vi.advanceTimersByTimeAsync(60_000);
+      // Only the single mount fetch — no interval re-fetches.
+      expect(statusCalls(ctx)).toBe(1);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+});